how to express diameter symbol by c code?

as subject

double hit! to hit the middle button!

but ,my mouse is two buttons

as following:

strncpy( text, @O Φ , sizeof(text)-1 );

text2=strcat(text,dimvalue);

ProStringToWstring(line,text2);

ProArrayObjectAdd ((ProArray*)&p_texts, PRO_VALUE_UNUSED, 1,

line);

ProDimensionTextSet (&p_dims, p_texts);

//Φ is not displayed in drawing model.why??